A fuel cell power plant, particularly one suited to operate electric vehicles, may typically require approximately twelve liters of water, which is stored in an accumulator when the fuel cell power plant is shut down. Many utilizations of fuel cell power plants cause them to be shut down during sub-freezing temperatures. Prior attempts to insulate the water accumulator of a fuel cell power plant so that it will not freeze for several days at −20° C. (−36° F.) resulted in volumes on the order of 40 liters, which is excessive for many applications of fuel cell power plants, particularly in vehicles. As an alternative, the water accumulator in a fuel cell power plant may be provided with a rapid thaw heater. Since a rapid thaw internal heater requires distributing heating elements throughout the accumulator, a 12 liter accumulator with rapid thaw internal heating elements would require a volume on the order of 40 liters, which is excessive. Furthermore, the so-called rapid thaw heaters require several minutes to thaw the ice in the accumulator, which is unacceptable in vehicles, in the general case.
In U.S. Pat. No. 7,108,937, there is disclosed a proton exchange membrane (PEM) fuel cell stack utilizing vacuum insulation panels (VIPs) to insulate the entire stack, including providing external reactant gas manifolds and pressure plates with VIP insulation. However, the fuel cell power plant, even with an insulated stack, is still subject to rapid freezing at below freezing temperatures, and slow recovery.